This invention relates to ratchet-and-pawl type drive mechanisms such as used for tightening down and loosening threaded fasteners. More particularly, the invention relates to a fastening means with self-contained reversing ratchet drive that is particularly useful for securing doors, and especially doors that must be tightly secured to protect against unintentional release or against pressure or dangerous atmosphere on the other side. Although the invention is particularly adapted for use in securing doors on coal feeders such as those used in power plants, it is by no means limited to that application and has utility in the broad field of reversing ratchet drives.
In many coal-fired power plants, coal is stored in and supplied from overhead hoppers or bunkers and fed downwardly by gravity through feed control means to pulverizers, boiler stokers, cyclone burners, or other apparatus. The feed control means may be a gravimetric feeder that receives coal from the hopper and delivers the coal at a controlled rate as free-falling or separately flowing particles. A feeder adapted for this purpose, known as a gravimetric feeder, is described in U.S. Pat. No. 3,187,944, the disclosure of which is incorporated by reference herein and made a part hereof.
Typically, a gravimetric feeder has a small, positive pressure maintained therein and has heavy doors at each end that are tightly bolted shut with as many as eight separate fastening bolts. Because of the danger of explosion due to the coal dust entrained in the atmosphere within the feeder, the doors must be strong and be well-secured to the feeder housing.
While doors to such feeders have in the past been sufficiently strong and designed to be adequately secured to resist an explosion, workmen, after opening a door for access to the interior, frequently fail to secure all the bolts, and even occasionally only tighten down a few bolts just enough to keep the door in place. This presents a dangerous condition, since in the event of an explosion the door could blow off and injure nearby personnel.
The present invention greatly simplifies the procedure for securing the door and reduces the tendency of workers to fail to tighten down the bolts to the desired position. Also, the invention affords other features and advantages heretofore not obtainable.